The service, which covers Bedfordshire, Cambridgeshire, Essex, Hertfordshire, Norfolk and Suffolk, was criticised for almost two years before the governance review over its poor response times, particularly in rural areas.

'Performance was improving'

Ms Stockham, who began working on the trust's board last September, said: "I stepped down with a very heavy heart after careful consideration because I had genuinely believed up until the last couple of days that I could be part of the solution.

"Things were starting to turn around and the performance was improving, but the focus has become unrelentingly on us as individuals.

"I've stepped down in order that there can be a reconstitution of the board.

"Perhaps with a bit of space created, now at least two of us are not the issue, the trust can get on with the business of really turning things about."

The NHS trust board is made up of 11 voting members - six non-executive directors, including the chair and five executive directors.